1. Field of the Invention
This invention relates to scanning laser microscope systems and, specifically, to scanning laser microscope systems for enhanced inspection of samples, such as, birefringent materials or fluorescent objects.
2. Description of Related Art
For many years optical microscopes have been useful for examining fine details and structures in materials. Conventional microscopes typically use the kind of imaging in which the object is illuminated as a whole. Light transmitted through or reflected from the object is imaged into an intermediate image plane by an objective lens. This intermediate image plane is either viewed with an eyepiece or scanned with a TV camera.
One disadvantage of conventional microscopy results from scattered light from one point of the object arriving at the intermediate image plane in another part of the image, thus, degrading the contrast between parts of the image. This effect is minimized in scanning microscope systems.
Optical scanning microscopy illuminates the object on a point by point basis and the transmitted, reflected, stray or emitted light is measured for each consecutive point. An image is formed by combining the point by point brightness measurements into a suitable display means. With the advent of the laser the point by point resolution of optical scanning microscopy improved due to the ability to focus the single wavelength light of the laser to a smaller spot. For a more detailed discussion of scanning microscope systems, see Wilson and Sheppard, "Theory and Practice of Scanning Optical Microscopy," Academic Press, pages 3-9, 1984.
If the material being viewed is anisotropic, a series of complications arise. Light passing through an anisotropic material travels at different velocities in different directions. Polarized light is further affected by differences in the propagation velocity of light at different polarization angles.
A birefringent material can be triaxially anisotropic. Further, a birefringent material causing light to travel therethrough at different velocities for each axial direction refracts a beam of light in two different directions to form two rays. A converging beam of polarized light passing through a birefringent material, whether viewed in a conventional or scanning microscope, will cause interference pattern effects resulting in dark and bright "brushes" and "rings". Jenkins and White, in "Fundamentals of Optics," McGraw-Hill Book Co., pages 576-579, 1976, discuss this effect.
These variations in image brightness make detection of small anomalies, such as inclusions, crystal lattice dislocations, grain boundaries, vacancies, interstitials, etc., more difficult for the microscopist. Only those areas of the image having uniform brightness can be examined with acceptable results. Thus, only a small portion of an image may be useful for examination of an object, resulting in viewing the object repeatedly to cover a given area.
In the manufacture of electro-optical devices, knowledge of the quality of the substrate material is important to achieve high yields of functional devices at reasonable cost. In the manufacture of molecularly oriented polymers and other birefringent materials, knowledge of the quality of the material is similarly important.
A confocal laser scanning microscope differs from a conventional microscope by affording depth discrimination as well as improved resolution.
Fluorescence laser scanning microscopy offers many advantages over conventional fluorescence microscopy. Light can be concentrated on very small spots of the sample enabling the detection of small concentrations of fluorescent substances. Further, in conventional fluorescence microscopy, out of focus fluorescence can give a relatively strong interference with fluorescence from the sample layer in focus. Whereas, out of focus fluorescence in a confocal laser scanning microscope interferes only in a very limited way with the flurrescence of a sample layer in focus.
It is an object of the present invention to provide an improved scanning laser microscope system to assist in detecting or characterizing fine details and structures of materials or other samples.
It is a further object of the present invention to provide means for enhancing the light transmitted through, reflected from or emitted from the material or sample to increase the contrast between the material or sample and anomalies or areas of interest contained therein.
It is a further object of the present invention to provide a single scanning laser system capable of depth discrimination in an object and/or use in fluorescence microscopy.
It is another object of the present invention to provide very precise means for processing signals representative of light detected from a scanning beam passing through or being reflected from a material or other sample.